1. Field of the Invention
This invention relates generally to semiconductor manufacture. More particularly, the invention pertains to an improved semiconductor card and to improved methods and systems for fabricating the card.
2. State of the Art
One type of electronic assembly containing semiconductor components is generally referred to as a “card.” Examples of such “cards” include multimedia cards (MMC) such as used in digital cameras and the like, memory cards, smart cards, and personal computer memory card international association (PCMCIA) cards. In the industry, these types of cards are sometimes referred to collectively as “semiconductor cards,” “multimedia cards” or “daughter boards.”
Typically, a semiconductor card is formed from a substrate, which may be a thin, printed circuit board (PCB) upon which electronic components are mounted. Such components may include, for example, at least one semiconductor die and/or die package as well as resistors, capacitors, inductors and the like to form a desired circuitry. The substrate includes conductors for providing power supply and interconnection of the various components. Typically, the components are mounted on one side, i.e., the “circuit” side of the substrate, and are electrically interconnected to external contacts on the opposing side by interlevel conductors. The external contacts are arranged for electrical contact with a next level package, i.e., mother board. In use in an exemplary electronic apparatus, such as a digital camera, the card may be inserted into a slot or other receiver for interconnection with a motherboard and to provide, for example, flash memory for digitally recorded images.
Semiconductor cards are typically intended for repeated handling by the public, necessitating protection of the components from mechanical forces, moisture, radiation and stray electrical currents, etc. In addition, the surface materials of the card must be resistant to normal wear and tear. This is particularly true in peripheral portions of the card. In the industry, the semiconductor components and interconnecting conductors on the circuit side of a card substrate have typically been encapsulated by first applying “glob top” encapsulant. Then, a separately formed protective cover produced by injection molding is adhesively attached over the circuit side of the substrate to form the semiconductor card. However, use of a separately formed cover not only adds undesirable thickness to the card but requires additional process steps and is subject to deleterious detachment of the cover from the substrate. In addition, any variation in mounted component height and overlying glob top material will result in card thickness variation.
For most applications, it is desirable to make the card as thin as possible. The use of thin cards saves space within the equipment in which the card is used, as well as storage space, and a savings in encapsulation material is also realized.
A further requirement for semiconductor cards is that the peripheral outlines and card dimensions be as smooth and uniform as possible, so that proper effective insertion into a card receiver is assured. The edges should not have any burrs. Specifications on the peripheral outline and dimensions of semiconductor cards have been set by various industry standard setting bodies, e.g., PCMCIA.
In present methods of manufacture, components for several semiconductor cards are fabricated and wire bonded on a strip of, e.g., circuit board. The strip may be viewed as equivalent to the lead frame in die manufacture. The individual cards are then separated from the strip using a singulation process such as sawing. Often, singulation step produces slivers or burrs and may form card edges which are rough or sharp. These defects can adversely affect the peripheral outline, dimensions, appearance and use of the card.
The need exists for a semiconductor card having improved uniformity in peripheral outline, dimensions, appearance, edge smoothness and performance. A method for producing an improved semiconductor card with reduced expenditure of time and materials is needed. In addition, the desired method will produce a card with improved precision in peripheral outline, dimensions and appearance, and at lower cost.